Defective excision of pyrimidine dimers and interstrand DNA crosslinks in rad7 and rad23 mutants of Saccharomyces cerevisiae

Summary Excision of pyrimidine dimers and interstrand DNA crosslinks was examined in the deletion mutants rad7-1, rad23-1, and rad7-1 rad23-1. These mutants remove pyrimidine dimers and crosslinks much less efficiently than the RAD ⁺ strains; only 30–60% of pyrimidine dimers and 25–40% of crosslinks are removed even after prolonged incubation. The rad7 and rad23 mutations may represent defects in protein factors which increase the efficiency of the nicking enzyme complex or make chromatin more accessible to the nicking activity.     

Molecular species of membrane phospholipids containing arachidonic acid and linoleic acid contribute to the interindividual variability of red blood cell Na+-Li+ countertransport: In vivo and in vitro evidence

Summary Previous studies indicate a particular sensitivity of red blood cell Na⁺-Li⁺ countertransport activity to small variations in the fatty acid composition of membrane phospholipids. To assess whether the interindividual variability of Na⁺-Li⁺ countertransport is related to differences in the species pattern of erythrocyte phosphatidylcholine (PC) and phosphatidylethanolamine (PE) in vivo, the molecular species composition of PC and PE as well as the kinetics of Na⁺-Li⁺ countertransport were analyzed in parallel in normo- and hyperlipidemic donors. Both in diacyl PC and in diacyl-PE the species 160/204 and 160/182 were, respectively, positively and negatively related to the apparent maximal velocity of Na⁺-Li⁺ countertransport. The sum of all species with 204 at sn₂ of diacyl-PE exhibited a strong positive (r = 0.82, 2p < 0.001), and those containing 182 a negative correlation (r = –0.63, 2p < 0.01) to the transport activity. Essentially similar connections were observed between these species and the apparent affinity of the transport system for intracellular Na⁺. To evaluate whether the associations between molecular species of membrane phospholipids and Na⁺-Li⁺ countertransport activity were indicative of a causal relationship, the species 160/204-PC and 160/182-PC were selectively introduced into the erythrocyte membrane by means of the PC-specific transfer protein. Replacement of 11% of native PC by 160/182-PC inhibited the transport rate by about 25%. Exchange of 6 and 9% of PC with 160/204-PC, in contrast, accelerated the transport rate by 30 and 60%, respectively. The accordance between the in vivo relations and the results of the in vitro modification strongly suggests that elevations and reductions in the arachidonic acid and linoleic acid content of membrane PC and PE contribute to the interindividual variability of red blood cell Na⁺-Li⁺ counter-transport activity and its acceleration in hyperlipidemias.The authors wish to thank Dr. W.O. Richter (II. Medizinische Klinik, Klinikum Großhadern, Universität München) for selection of the patients and Dr. T. Brosche (Universität ErlangenNürnberg) for gaschromatographic analyses. This study was supported in part by a grant of the Wilhelm-Sander-Stiftung to B.E.     

Discussion: Phylogenetic Species Concept: Pluralism, Monism, and History

Species serve as both the basic units of macroevolutionary studies and as the basic units of taxonomic classification. In this paper I argue that the taxa identified as species by the Phylogenetic Species Concept (Mishler and Brandon 1987) are the units of biological organization most causally relevant to the evolutionary process but that such units exist at multiple levels within the hierarchy of any phylogenetic lineage. The PSC gives us no way of identifying one of these levels as the privileged level on which taxonomic classifications can be based.     

Host size and sex allocation of parasitoids in a gall forming community

Summary The sex ratios of three Mesopolobus species were found to vary in different hosts in a gall-forming community in Berkshire. These relationships were consistent with Charnov's host size—sex ratio hypothesis (Charnov 1979). Due to the segregation of host species on different species of Quercus, it was possible to conduct a geographical variation experiment proposed by Charnov et al. (1981). The results of this experiment suggest that the parasitoids have a fixed rule of thumb and are not flexible in their sex allocation in response to changes in host size distribution. The data, therefore, do not support the prediction of Charnov's hypothesis. Problems associated with this kind of field experiment are discussed.     

Specialized and generalized dispersal systems: where does ‘the paradigm’ stand?

I explore the specialization versus generalization paradigm in frugivory and seed dispersal. This view predicts that some tropical trees produce nutritious fruits adapted for use by a small coterie of specialized frugivores that provide reliable seed dissemination. Other tree species are expected to offer superabundant fruits of lower nutritional reward, relying instead on common opportunistic frugivores that are individually less reliable, but collectively disperse seeds effectively. Though widely referenced, many aspects of the paradigm are untested with tropical trees and avian frugivores, primarily because plant ecologists rarely determine whether specialist or generalist foragers are responsible for different patterns of seed distribution, while students of foraging behavior rarely determine the effects seed dispersal by different animals for survival of seeds or seedlings of specialist or generalist trees.Ecological paradigms provide alternative hypotheses, without evolutionary arguments. Keystone species have ecological effects disproportionate to their abundance; it is important for management considerations to know whether fruiting trees or frugivores serve as keystone mutualists in tropical forests. Alternatively, the extent to which vertebrate seed dispersers influence density-dependent seed, seedling, sapling, or adult mortality may have important consequences for spatial dispersion and population dynamics of tree species in tropical forests.     

Bat species diversity in a lake archipelago in central Sweden

The bat fauna of 35 islands in a large lake in central Sweden were examined using ultrasound detectors. We tested the hypothesis that there is no difference in species number between the mainland and the island fauna. Eight species were found. Species numbers were analysed against island area, area of some habitats (coniferous forest, deciduous forest, semi-open habitats and open habitats), degree of isolation (distance from mainland and from stepping stones) and time spent searching for bats. Species number increased with area of deciduous forest. Presence of houses tended to increase species number. There seems to be a negative relationship between species number and degree of isolation (nearly significant). The results suggest that at least three species, Myotis brandti (Eversmann, 1845), M. mystacinus (Kuhl, 1819) and Plecotus auritus (Linnaeus, 1758), are negatively affected by forest patchiness. These species occurred mainly on large islands. Thus, the results do not support the hypothesis. The reasons why some species avoid open habitats are discussed.     

Preparation and heteronuclear 2D NMR spectroscopy of a DNA dodecamer containing a thymidine residue with a uniformly 13C-labeled deoxyribose ring

Summary [¹³C₅]-2-Deoxy-d-ribose, synthesized from [¹³C₆]-d-glucose (98% ¹³C), was coupled with thymine to give [1,2,3,4,5-¹³C₅]-thymidine (T) in an 18% overall yield. The thymidine was converted to the 3-phosphoramidite derivative and was then incorporated into a dodecamer 5-d(CGCGAATTCGCG)-3 by solid-phase DNA synthesis. Preparation of 0.24 mole of the labeled dodecamer, which is sufficient for a single NMR sample, consumed only 25 mg of glucose. By virtue of the ¹³C labels, all of the ¹H-¹H vicinal coupling constants in the sugar moieties were accurately determined by HCCH-E.COSY.     

Mutational specificity of ethyl methanesulfonate in excision-repair-proficient and -deficient strains of Drosophila melanogaster

Summary The vermilion gene was used as a target to determine the mutational specificity of ethyl methanesulfonate (EMS) in germ cells of Drosophila melanogaster. To study the impact of DNA repair on the type of mutations induced, both excision-repair-proficient (exr ⁺) and excision-repair-deficient (exr ^–) strains were used for the isolation of mutant flies. In all, 28 mutants from the exr ⁺ strain and 24 from the exr ^– strain, were characterized by sequence analysis. In two mutants obtained from the exr ⁺ strain, small deletions were observed. All other mutations were caused by single base-pair changes. In two mutants double base-pair substitutions had occurred. Of the mutations induced in the exr ⁺ strain, 22 (76%) were GCAT transitions, 3 (10%) ATTA transversions, 2 (6%) GCTA transversions and 2 (6%) were deletions. As in other systems, the mutation spectrum of EMS in Drosophila is dominated by GCAT transitions. Of the mutations in an exr ^– background, 12 (48%) were GCAT transitions, 7 (28%) ATTA transversions, 5 (20%) GCTA transversions and 1 (4%) was a ATGC transition. The significant increase in the contribution of transversion mutations obtained in the absence of an active maternal excision-repair mechanism, clearly indicates efficient repair of N-alkyl adducts (7-ethyl guanine and 3-ethyl adenine) by the excision-repair system in Drosophila germ cells.     

Dinuclear versus mononuclear ruthenium(II) and osmium(II) complexes as potent mediators of glucose oxidase; crystal structure of [OsCl(4,4′-bpy)(bpy)<Subscript>2</Subscript>]BF<Subscript>4</Subscript>

New and known homo- and heterodinuclear Ru^II and Os^II complexes with 4,4-bipyridine (4,4-bpy), pyrazine, and 4-pyCH=CHpy-4 as bridging ligands (LL) of the type [Cl(bpy)₂M(LL)MCl(bpy)₂]X₂ (bpy=2,2-bipyridine; X=PF₆ or BF₄) have been studied in their capacity to exchange electrons with a reduced active site of glucose oxidase (GO) from Aspergillus niger. Cyclic voltammograms (CVs) of the dimers in the aqueous buffered solution, when compared with CVs of the parent monomeric species [MCl(LL)(bpy)₂]BF₄ and [MCl₂(bpy)₂] which could be generated at pH7, if the dimers undergo monomerization, indicate that the dimers are the dominating species under such conditions. All electrochemically oxidized dinuclear complexes studied show high rates of oxidation of GO reduced by d-glucose and the corresponding observed second-order rate constants are in the range (5–64)×10⁵ M^–1 s^–1 at 25 °C. However, these values are lower than that for the mononuclear complex [OsCl(4,4-bpy)(bpy)₂]BF₄ (1.1×10⁷ M^–1 s^–1), suggesting that potentially two-electron dimeric mediators have no advantage compared with corresponding monomeric complexes of Ru^II and Os^II. The structure of [OsCl(4,4-bpy)(bpy)₂]BF₄ was confirmed by X-ray crystallography. The monodentate 4,4-bpy ligand is coordinated cis to the chloride. Its higher reactivity toward reduced GO is accounted for in terms of the antenna effect of the monodentate 4,4-bpy ligand. The antenna length equals 9.2 Å and matches the depth of the enzyme active site pocket of ca. 10 Å. The mechanism of the antenna effect is discussed     

A new and phylogenetically suggestive morphotype ofKeratella lenzi (Rotifer,Monogononta), from Argentina

The morphological characteristics ofKeratella lenzi (f.ayui) f. nov. and the phylogenetic and ecological implications of the appearance of posterolateral spines inK. lenzi Hauer, 1953 are discussed. The morphotype is described after detailed observations using light and scanning electron microscopy, and compared with otherKeratella species of the superspecies valga. The pores of the lateral antennae are described, and proposed as a new character for future comparative research. Some ecological information is also given.     

Extensive variation at the α-glycerophosphate dehydrogenase locus in species of waterstriders (Gerridae: Hemiptera)

Variation at the -glycerophosphate dehydrogenase (-Gpdh; EC 1.1.1.8) locus was surveyed in 11 species of waterstriders (Gerridae: Hemiptera) and five other species of aquatic Hemiptera. Species of waterstriders exhibited considerable inter- and intraspecific variation in degree of winglessness. Average heterozygosity (0.401±0.090) and average number of observed electromorphs (5.36±0.96) for the 11 gerrid species were well above values reported for nearly all other insect species surveyed to date. Wing-monomorphic and wing-polymorphic species did not differ in average -Gpdh heterozygosity. Of the three wing-polymorphic species surveyed geographically, two species exhibited marked variation in wing-morph frequencies but homogeneous -Gpdh allele frequencies. The third species exhibited geographically homogeneous -Gpdh and wing-morph frequencies, but no significant association between -Gpdh phenotype and wing morph was observed in any surveyed population. These results are consistent with hypotheses evoking either relaxed purifying selection at the -Gpdh locus in species of Gerridae due to the apparent reduced importance of flight, or selective maintenance of common -Gpdh electromorphs.This work was supported by NSF Grant DEB 76-20967 to Alan H. Brush, funds from the Research Foundation of the University of Connecticut to Carl W. Schaefer, and USPHS Grant GM 21133 to Richard K. Koehn.     

A methodological approach to the use of terrestrial invertebrates for the assessment of alluvial wetlands

We review progress toward developing a data-analysis system using invertebrate species lists in wetland evaluation procedures. Species lists for Mollusca, Carabidae (Coleoptera), Empidoidea and Syrphidae (Diptera), derived from samples collected at six stations along a transect established at a site on the floodplain of the River Loire (France) provide the raw data. An initial analysis using a traditional ordination method (Correspondence Analysis) is carried out. A data base was established for the 118 mollusc, carabid and syrphid species recorded, and each species was then treated not as a simple integer, but as an amalgam of digitised attributes deemed responsive to wetland conditions, in a correspondence analysis on instrumental variables. Despite the generalized nature of the attributes as defined for this example, the approach demonstrates a marked increase in interpretability of the output of analysis, in respect of the relation between the species and the floodplain environment. It also highlights the value of use of data pertaining to more than one taxonomic group and of selecting these taxonomic groups on the basis of complementarity of their bioindicator potential.Corresponding Editor: J.T.A. Verhoeven     

Ultrastructure of paraspermatozoa of cerithiacean gastropods (prosobranchia: Mesogastropoda)

Using transmission electron microscopy, paraspermatozoa of representative species of the families Cerithiidae, Potamididae, Planaxidae, Dialidae and the genusAustralaba (family position uncertain) have been examined and compared with those produced by other prosobranchs, particularly other investigated cerithiaceans. Special attention is focused on the phylogenetic importance of paraspermatozoa and euspermatozoa within the superfamily Cerithiacea. The paraspermatozoa of cerithiacean gastropods fall into two structural categories: (1) those with a head region and a tail tuft (number of tails and the length of the tail tuft variable — Cerithiidae, Planaxidae, Potamididae, Modulidae, Turritellidae, Campanilidae, Pleuroceridae,Obtortio, Australaba); and (2) those with an elongate, vermiform body filled with large electron-dense vesicles and up to ninety axonemes — the latter emerging as numerous short tails from the posterior half of the paraspermatozoon body (Dialidae).     

Plant and insect diversity along a pollution gradient: understanding species richness across trophic levels

We analysed species richness of plants and true bugs (Insecta, Heteroptera) along a pollution gradient in Scots pine stands in Central Germany. As a consequence of particulate deposition, pH-values of soils increased in the vicinity of the emission source. Therefore, emission increased productivity. Species richness of plants increased with decreasing distance from emission source, and thus with increasing productivity. Similarly, species richness of herbivorous Heteroptera increased with decreasing distance from emission source, whereas, surprisingly, abundance decreased. The proportion of specialised herbivorous bug species is largest in the vicinity of the emission source. Thus, the diversity pattern of herbivores may be explained by the specialisation hypothesis and not the consumer rarity hypothesis. Species richness and abundance of carnivorous Heteroptera showed no significant trend along the gradient. Overall our data favour the bottom-up control of species diversity in the analysed system.     

Species diversities analyzed by density and cover in an early volcanic succession

To evaluate alpha diversities, various variables such as density, cover, volume, and weight have been used. However, density is often a distinct variable from the remaining three. To clarify differences in diversity measured by those two kinds of variables, the data collected in fourteen 2×5 m permanently-marked plots on Mount Usu, Japan, which erupted during 1977 and 1978 in growing seasons from 1983 to 1989 was analyzed, using Shannon's species diversity (H) that is represented as a result of combination of species richness and evenness (J). H and J were evaluated by density (density H and J) and cover (cover H and J). Cover H and J were significantly lower than density H and J, indicating that cover H has different characteristics from density H. Those differences are due to differences in evenness, because species richness is the same. The rank orders of species density are different from those of cover. The predominance of a few perennial herbs greatly decreases cover evenness, while seedling establishment success influences density evenness. Therefore, I propose that, during the early stages of succession on harsh environments such as volcanoes, density diversity represents seedling establishment success rate while cover diversity expresses vegetative reproduction success rate.     

Energy migration in purple bacteria. The criterion for discrimination between migration- and trapping-limited photosynthetic units

A criterion has been evolved for distinguishing between migration- and trapping-limited photosynthetic units (PSUs). Its application to purple bacteria has proved their PSUs to be of trapping-limited type. It means that any improvements of the molecular structure of their PSUs cannot noticeably increase the overall rate constant of excitation delivery from antenna BChls to reaction centers (RCs).Abbreviations PSUs photosynthetic units - RCs reaction centers - Chl chlorophyll - BChl bacteriochlorophyll - R intermolecular distance, _e - quantum yields of the primary excitation trapping and wasteful losses respectively - _fl excitation and fluorescence lifetimes respectively     

Molecular profiling of tyrosine kinases in normal and cancer cells

As the post-genome era is approaching, with vast amount of sequence information available and new technology developed, scientists are presented with opportunities to explore in simple analysis the structure and expression pattern of not just a single gene, but of an entire family of genes, if not the entire genome. The concept of molecular profiling or expression array has thus emerged. The need to simultaneously see all genes in the same family is obvious under the precept of the combinatorial process being an underlying principle of complex biological systems: no gene exists in isolation, for virtually every molecule participates in intermolecular interactions. The activation of receptor tyrosine kinases through homo or hetero-dimerization is the prototypic example. In this review, a tyrosine kinase profile technique and its application to studying the expression of tyrosine kinases and the identification of novel kinases will be discussed. This serves as an introduction to the several interesting papers published in this special kinase issue of theJournal of Biomedical Sciences, using this technique. A new simplified approach, kinase display, which is an extension of the profiling method and requires only restriction digestion and gel analysis will also be introduced.     

Hexahydroindanone derivatives of steroids formed by Rhodococcus equi

Summary A mutant strain of Rhodococcus equi accumulates three metabolites from the androst-4-ene-3,17-dione or from its degradation intermediate, 3a-H-4(3'-propionic acid)-7a-methylhexahydro-1,5-indanedione (MEPHIP). These three metabolites are: 3a-H-4a(3'-propionic acid)-5-hydroxy-7a-methylhexahydro-1-indanone--lactone (HIL); 3a-H-4(3'-trans acrylic acid)-5-hydroxy-7a-methylhexahydro-1-indanone (^2'-5-hydroxy-MEPHIP); and 3a-H-4(3'-hydroxy-3'-propionic acid)-5-hydroxy-7a-methylhexahydro-1-indanone (3'-hydroxy-HIL). The behaviour of this mutant allows us to propose a pathway for degradation of the intermediates, methylperhydroindanone propionates. However, during this degradation, the side-chain propionate was eliminated by a-oxidation mechanism. Offprint requests to: A. Miclo     

High-level Expression of Maize <Emphasis Type="Italic">γ</Emphasis>-zein Protein in Transgenic Soybean (<Emphasis Type="Italic">Glycine max</Emphasis>)

Primers were developed for 118 microsatellites isolated from grape (Vitis vinifera) genomic libraries enriched for (AC)n repeats. Only one microsatellite sequence matched other grape SSR-sequences in the GeneBank database. Genotyping was carried out in the parental lines and four offspring of two pseudo-test-cross populations, Cabernet Sauvignon x Seyval and Chardonnay x Bianca, and a further six other grape genotypes (V. vinifera Sultanina, Merlot, Syrah, Müller-Thurgau, Vitis Regent and V. riparia Gloire de Montpellier). A total of 108 microsatellites showed easily scorable alleles and 100 of them segregated according to a configuration suitable for mapping in either cross. A further 8 SSRs, although unsuitable for mapping in those crosses, showed polymorphism in the other genotypes tested. This set of markers was used, along with 75 microsatellites of other repeat-types, to fingerprint 46 offspring of the cross Chardonnay x Bianca. For each full-sib, individual heterozygosity and distance in repeat units between pairs of alleles at each locus (mean d²) were calculated as a tool for predicting highly outbred recombinant individuals. Six microsatellites with segregation ratios significantly distorted towards the lack of homozygous sibs were identified and mapped to linkage groups LG 3 and LG 5. Estimation of heterozygosity at genome-wide level and genotyping at loci for which homozygous sibs are discriminated against are discussed for marker-assisted background selection in outcrossing grapevines.     

Ethnobotany of seaweeds: clues to uses of seaweeds

Extensive uses of fresh and dried seaweeds by coastal populations over the world can furnish clues to potential food and other uses of seaweeds, just as the first extraction of a seaweed gelatin now used for bacteriological purposes was discovered by a housewife in search of a pudding. Ethnic uses as food depend heavily on closely related species suitable for making cool, gelatinous dishes or concoctions, or on species suitable for adding to soups or stews. Rarely, single species like cochajugo (Durvillea antarctica) in Chile and rimu (Durvillea antarctica) in New Zealand point to different kinds of food preparation. Oriental cuisine incorporates many different species of seaweeds in a wide variety of ways, whereas commercial western uses depend upon extracts of wall materials to suspend, emulsify or stabilize a broad variety of foods and products.